JP2009188142A - Epoxy resin tablet for semiconductor sealing, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method in which epoxy resin tablets for semiconductor sealing which have superior flowability and moldability in sealing of a semiconductor element can be successively manufactured while cracking, chipping and scattering of powder of an epoxy resin composition during conveyance can be suppressed. <P>SOLUTION: The manufacturing method of epoxy resin tablets for semiconductor sealing includes a process of obtaining a molding 2 by making a tablet of an epoxy resin composition for semiconductor sealing, and a process of forming a surface coating 3 of 5 to 50 μm in average thickness on a surface of the molding using polyethylene wax. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an epoxy resin tablet for semiconductor encapsulation formed by tablet-molding an epoxy resin composition for semiconductor encapsulation into a tablet and a method for producing the same.

  When a semiconductor element such as a transistor, IC, LSI or the like is encapsulated with an epoxy resin composition, a transfer molding method is generally used. In such a transfer molding method, a tablet composed of an epoxy resin composition is generally used. Such a tablet includes, for example, an epoxy resin, a phenol resin curing agent, a curing accelerator, a release agent, a flame retardant, a colorant, and the like. A blend of 50 to 90% by weight of the total inorganic filler is mixed with a mixer, and this is formed into a sheet by a roll or an extruder, and further pulverized into a powder using a hammer mill or the like. Manufactured by tableting into tablets.

  However, since the tablet manufactured in this way is tablet-molded only by mechanical compression, the mechanical strength is not sufficient, and the tablet is transported from the tablet-molded place to the sealed place. Cracks and chipping occur. For this reason, the powder of an epoxy resin composition is heated at the time of tableting, or it is heated after tableting (for example, refer patent document 1).

Further, when tableting, a part of the powder of the epoxy resin composition may adhere to the tableting surface of the tablet mold, and the tablet may be smeared. When a semiconductor element is sealed using a tablet with such a glare, a void or the like is generated in the sealed portion, and the reliability of the product is lowered. In addition, when tableting, the powder of the epoxy resin composition may be scattered, resulting in deterioration of the working environment, contamination of equipment, and reduction of product reliability. For this reason, a tablet mold is preheated and a semi-molten resin layer is formed on the surface layer of the tablet (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 3-178405 JP-A-4-340236

  As described above, in order to suppress tablet breakage or chipping during transportation, tablet sag during production, or scattering of the epoxy resin composition powder, or when tableting the powder of the epoxy resin composition or tableting After being formed, heating is performed, and the tablet mold is preheated. However, with respect to such a method, it is difficult to continuously manufacture due to contamination of the tablet mold, and the fluidity and moldability of the tablet when sealing the semiconductor element are not always satisfactory. It is not going to go.

  The present invention has been made in order to solve such problems, and is capable of suppressing cracking, chipping, and scattering of powder of the epoxy resin composition during transportation, and fluidity when sealing a semiconductor element. It aims at providing the manufacturing method which can manufacture continuously the epoxy resin tablet for semiconductor sealing which is excellent also in a moldability. In addition, the present invention is an epoxy resin tablet for semiconductor encapsulation that has excellent fluidity and moldability when sealing semiconductor elements, as well as cracking, chipping, and scattering of powder of the epoxy resin composition during transportation are suppressed. The purpose is to provide.

  The manufacturing method of the epoxy resin tablet for semiconductor sealing of the present invention includes a step of tableting the epoxy resin composition for semiconductor sealing into a tablet to obtain a molded body, and using polyethylene wax on the surface of the molded body And a step of performing surface coating with an average thickness of 5 μm or more and 50 μm or less.

  In the manufacturing method of the epoxy resin tablet for semiconductor encapsulation of this invention, it is preferable that the acid value of the said polyethylene wax is 10 mgKOH / g or more and 30 mgKOH / g or less, and a number average molecular weight is 1000 or more and 5000 or less.

  Moreover, the epoxy resin tablet for semiconductor encapsulation of the present invention is a tablet-like molded article made of an epoxy resin composition for semiconductor encapsulation, and an average thickness of 5 μm or more and 50 μm made of polyethylene wax formed on the surface of the molded article. It has the following surface coating layers.

  In the epoxy resin tablet for semiconductor encapsulation of the present invention, the polyethylene wax preferably has an acid value of 10 mgKOH / g to 30 mgKOH / g and a number average molecular weight of 1000 to 5000.

  According to the method for producing an epoxy resin tablet for semiconductor encapsulation of the present invention, an epoxy resin composition for semiconductor encapsulation is tablet-molded into tablets, and then an average thickness of 5 μm or more and 50 μm or less using polyethylene wax on the surface thereof. By applying the surface coating, cracking, chipping, and scattering of the powder of the epoxy resin composition are suppressed in the middle of conveyance, and the epoxy for semiconductor encapsulation has excellent fluidity and moldability when sealing semiconductor elements. Resin tablets can be manufactured continuously.

  Moreover, according to the epoxy resin tablet for semiconductor encapsulation of the present invention, a surface coating layer having an average thickness of 5 μm or more and 50 μm or less made of polyethylene wax is formed on the surface of the tablet-like molded body made of the epoxy resin composition for semiconductor encapsulation. By providing, it is possible to suppress cracks and chips during conveyance, and scattering of the powder of the epoxy resin composition, and excellent fluidity and moldability when sealing the semiconductor element.

  Hereinafter, the present invention will be described in detail. The manufacturing method of the epoxy resin tablet for semiconductor encapsulation of the present invention includes a step of tablet-molding the epoxy resin composition for semiconductor encapsulation into a tablet shape to obtain a molded body, and using polyethylene wax on the surface of the molded body And a step of performing a surface coating with an average thickness of 5 μm or more and 50 μm or less.

  The epoxy resin composition for semiconductor encapsulation used in the present invention (hereinafter simply referred to as an epoxy resin composition) contains an epoxy resin as an essential component, and in addition, for example, a phenol resin curing agent, a curing accelerator, and inorganic filling. It contains materials and the like. In addition, the epoxy resin composition used for this invention is not necessarily limited to such a thing.

  Examples of the epoxy resin include monomers, oligomers, and polymers generally having two or more epoxy groups in one molecule, and the molecular weight and molecular structure are not particularly limited. For example, biphenyl type epoxy resin, bisphenol type epoxy Resin, stilbene type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenolmethane type epoxy resin, alkyl modified triphenolmethane type epoxy resin, triazine nucleus-containing epoxy resin, dicyclopentadiene modified phenol type epoxy resin, A phenol aralkyl type epoxy resin (having a phenylene skeleton, a biphenylene skeleton, or the like), a naphthol type epoxy resin, or the like may be used, and these may be used alone or in combination of two or more.

  Examples of the phenol resin curing agent include monomers, oligomers, and polymers generally having two or more phenolic hydroxyl groups in one molecule, such as phenol novolac resin, cresol novolac resin, dicyclopentadiene modified phenol resin, terpene modified phenol resin, Examples thereof include a triphenolmethane type resin, a phenol aralkyl resin (having a phenylene skeleton, a biphenylene skeleton, and the like), a naphthol aralkyl resin, and the like. These may be used alone or in combination of two or more. In addition, from the viewpoint of improving the moisture resistance reliability and heat resistance reliability of the cured product, phenol novolak resin, dicyclopentadiene modified phenol resin, phenol aralkyl resin, naphthol aralkyl resin, terpene modified phenol resin and the like are particularly preferable. It is done.

  The content of the phenol resin curing agent is such that the ratio of the number of epoxy groups of the epoxy resin to the number of phenolic hydroxyl groups of the phenol resin curing agent (the number of epoxy groups of the epoxy resin / the number of phenolic hydroxyl groups of the phenol resin curing agent) is 0.8 or more. It is preferable to be 3 or less. If the ratio is less than 0.8, the moldability of the epoxy resin composition or the electrical properties of the cured product may be reduced. If the ratio exceeds 1.3, the moisture resistance reliability of the cured product is not sufficient. There is a fear.

  If a hardening accelerator accelerates | stimulates hardening reaction with an epoxy resin and a phenol resin hardening | curing agent, a molecular structure, molecular weight, etc. will not be specifically limited, For example, DBU (1,8-diazabicyclo (5.4. 0) undecene-7), trimethylphosphine, triethylphosphine, tributylphosphine, triphenylphosphine, tri (p-methylphenyl) phosphine, tri (nonylphenylphosphine), methyldiphenylphosphine, dibutylphenylphosphine, tricyclohexylphosphine, 1, Organic phosphine compounds such as 2-bis (diphenylphosphino) ethane and bis (diphenylphosphino) methane, 2-methylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, - phenyl-4-methylimidazole, 2-imidazole compounds of heptadecyl imidazole, or include these derivatives, they may be used alone or may be used as a mixture of two or more.

  Since the content of the curing accelerator is different in each catalyst activity, a suitable amount thereof cannot be generally determined, but is preferably 0.1% by mass or more and 5% by mass or less based on the entire epoxy resin composition. . When the content of the curing accelerator is less than 0.1% by mass, the curing performance is inferior, while when it exceeds 5% by mass, the moisture resistance reliability may be deteriorated.

  Examples of the inorganic filler include fused silica pulverized by a ball mill or the like, spherical silica obtained by flame melting, spherical silica produced by a sol-gel method, crystalline silica, alumina, boron nitride, aluminum nitride, silicon nitride, Examples thereof include magnesia and magnesium silicate. These may be used alone or in combination of two or more. When the semiconductor element to be sealed is an element that generates a large amount of heat, alumina, boron nitride, aluminum nitride, silicon nitride, or the like having a thermal conductivity as large as possible and a low thermal expansion coefficient is preferable. These may be blended with fused silica or the like. The shape of the inorganic filler is not particularly limited, and flakes, dendrites, spheres and the like can be used alone or in combination, but from the viewpoint of low viscosity and high filling, they are spherical. Is preferred.

  The epoxy resin composition used in the present invention is further provided with a low stress agent such as powders such as silicone rubber and silicone gel, silicone-modified epoxy resins and phenol resins, and thermoplastic resins composed of methyl methacrylate-butadiene-styrene. Flame retardants and flame retardant aids such as brominated epoxy resins and antimony oxide, colorants such as carbon black, nonionic surfactants, fluorine surfactants, wetting improvers such as silicone oils, antifoaming agents, etc. It can mix | blend suitably as needed.

  The epoxy resin composition used in the present invention is blended with, for example, the above-described epoxy resin, phenol resin curing agent, curing accelerator, inorganic filler, and other additives, kneaded, cooled, and then pulverized. Can be obtained.

  Examples of the kneading apparatus used for kneading include a co-rotating twin screw extruder, and the shape and material of the screw and cylinder to be used are not particularly limited. High wear resistance is desirable. Moreover, at the time of kneading | mixing, it is preferable that the temperature of an epoxy resin composition shall be the range of 70 to 120 degreeC. When the temperature of the epoxy resin composition at the time of kneading is less than 70 ° C., for example, the appearance of the extruded granulated product becomes a crumpled shape, the powder of the epoxy resin composition is easily scattered, and is further obtained by tableting. Air bubbles tend to remain inside. On the other hand, when the temperature of the epoxy resin composition at the time of kneading exceeds 120 ° C., the fluidity when sealing the semiconductor element is lowered, and the moldability is lowered. Further, the kneaded product thus obtained can be pulverized using a known pulverizing apparatus such as a hammer mill.

  The powdery epoxy resin composition thus produced is formed into a molded body by tableting into a tablet using a tableting machine. As the tableting machine, a known single-shot or rotary tableting machine can be used. A predetermined amount of the epoxy resin composition is put into the tableting mold (tablet mold) and compressed so as to be compressed. A molded product can be obtained by tablet molding.

  In the present invention, the surface of the molded body thus produced is subjected to surface coating using polyethylene wax. By performing such surface coating, it is possible to suppress cracking, chipping, and scattering of the epoxy resin composition powder during conveyance. Further, by using polyethylene wax for the surface coating, the fluidity when sealing the semiconductor element can be made appropriate, and the moldability can be made good. Furthermore, the surface coating is performed after the molded body is manufactured, so that contamination of the tableting mold can be suppressed and the molded body can be continuously produced.

  Such surface coating may be performed on at least a part of the surface of the molded body. For example, the surface coating may be performed only on the upper surface, only the side surface, or only the upper surface and the side surface of the molded body. It is preferable to be performed on the entire surface.

  At this time, the surface coating is performed so that the average thickness in a final state obtained by drying or the like is 5 μm or more and 50 μm or less. When the thickness of the surface coating is less than the above lower limit value, the coating amount is too small, and the scattering of the powder of the epoxy resin composition during the conveyance may not be effectively suppressed. On the other hand, when the thickness of the surface coating exceeds the above upper limit, the coating amount is too large, the fluidity when sealing the semiconductor element becomes inappropriate, the moldability may be reduced, and the semiconductor element or There is a risk that the adhesion with the frame or the like will be reduced, and the appearance of the product will also be reduced.

  The thickness of the surface coating is obtained by cutting and polishing the surface-coated molded body (tablet), and measuring the distance from the surface portion of the molded body to the surface portion of the surface coating using a microscope on this cut and polished surface. Can be confirmed. Further, the average thickness of the surface coating can be calculated as the average value of the surface coating thicknesses measured at any five locations in this way.

  The surface coating method for the molded body is not necessarily limited, and can be performed by applying a known method such as a curtain coating method, a dip coating method, or a spray coating method. It is preferable to apply a spray coating method that can ensure uniformity and easily adjust the thickness.

  For example, in the spray coating method, polyethylene wax is adjusted to an appropriate concentration and viscosity using a hydrocarbon-based volatile solvent to form a coating liquid, and this coating liquid is sprayed from the nozzle toward the molded body. Surface coating can be performed by volatilizing and removing the volatile solvent of the coating liquid. At this time, for example, the thickness of the surface coating can be appropriately adjusted by changing the concentration and viscosity of the coating solution, or by changing the time, distance, and the like of spraying the coating solution toward the molded body.

  The volatile solvent used for preparing the coating liquid is not particularly limited as long as it can be volatilized and removed during spray coating and can dissolve polyethylene wax. However, a hydrocarbon-based volatile solvent such as n-heptane is preferably used.

  Further, the polyethylene wax used for surface coating including such a spray coating method is not necessarily limited. For example, the acid value is 10 mgKOH / g or more and 30 mgKOH / g or less, and the number average molecular weight is 1000 or more and 5000. The following are preferably used.

  When the acid value of the polyethylene wax is less than the above lower limit value, phase separation occurs between the epoxy resin matrix, and the mold is soiled when the semiconductor element is sealed. There is a possibility that the adhesive force is lowered and the appearance of the product is also lowered. On the other hand, if the acid value of the polyethylene wax exceeds the upper limit, compatibility with the epoxy resin matrix is too good, and there is a possibility that sufficient releasability cannot be ensured when sealing the semiconductor element.

  Moreover, when the number average molecular weight of the polyethylene wax is less than the lower limit, the affinity with the epoxy resin matrix is increased, and there is a possibility that sufficient releasability cannot be secured when the semiconductor element is sealed. On the other hand, if the number average molecular weight of the polyethylene wax exceeds the above upper limit value, phase separation occurs between the epoxy resin matrix, the mold is soiled when the semiconductor element is sealed, the semiconductor element, the frame, etc. There is a possibility that the adhesive strength with and the appearance of the product will also deteriorate.

  In addition, the acid value of polyethylene wax is measured according to the method prescribed | regulated to JISK5601, and the number average molecular weight is measured by a gel permeation chromatography (GPC) method.

  FIG. 1 is an external view showing the tablet 1 of the present invention manufactured as described above. The tablet 1 has a molded body 2 made of an epoxy resin composition, and a surface coating layer 3 made of polyethylene wax formed on the surface of the molded body 2. The surface coating layer 3 has an average thickness of 5 μm or more and 50 μm or less. For example, the surface coating layer 3 is formed on the entire upper surface, side surface, and lower surface of the molded body 2. In addition, although the tablet 1 is generally cylindrical as shown in the figure, it is not necessarily limited to such a shape.

  The tablet 1 manufactured in this manner is suitably used for transfer molding for sealing a semiconductor element. Examples of the semiconductor element to be sealed include an integrated circuit, a large-scale integrated circuit, a transistor, a thyristor, and a diode, but are not necessarily limited to these. Moreover, as a shaping | molding condition, a normal shaping | molding condition can be employ | adopted, for example, the conditions for 1 to 5 minutes are employable at the temperature of 165 degreeC or more and 185 degrees C or less.

  Hereinafter, the present invention will be specifically described with reference to examples. The present invention is not limited to these examples.

Example 1
As an epoxy resin composition, orthocresol epoxy resin (ESCN-195, manufactured by Sumitomo Chemical Co., Ltd.) 6.4% by mass, phenol aralkyl resin (MEH-7800M, manufactured by Meiwa Kasei Co., Ltd.) 5.6% by mass, imidazole-based curing Accelerator (C17Z-T, manufactured by Shikoku Kasei Kogyo Co., Ltd.) 0.3% by mass, fused silica powder (FB105, manufactured by Denki Kagaku Kogyo Co., Ltd.) 87% by mass, carnauba wax 0.2% by mass, Carbon black (MA-600, manufactured by Mitsubishi Chemical Corporation) 0.15% by mass and n-amino 3-propyltrimethoxysilane (KBM-602, manufactured by Shin-Etsu Chemical Co., Ltd.) are mixed at room temperature, and 90 to 95 ° C. After being heat-kneaded in the above range, a cooled and pulverized product was prepared.

  A predetermined amount of this epoxy resin composition was put into a mortar (mold temperature: 26 ° C.) of a rotary type tableting machine and compressed by a punch to form a tablet. On the other hand, n-heptane as a volatile solvent was added to polyethylene wax (acid value 10 mgKOH / g, number average molecular weight 3000, product number HW-4252E, manufactured by Mitsui Chemicals, Inc.) to adjust the viscosity and concentration to obtain a coating solution. . Then, the coating liquid was spray-coated on the molded body, and the volatile solvent was dried and removed to form a surface coating layer having an average thickness of 10 μm, and a tablet as a sample was manufactured.

(Example 2)
N-heptane as a solvent was added to polyethylene wax (acid value 60 mgKOH / g, number average molecular weight 1500, product number HW-1105A, manufactured by Mitsui Chemicals, Inc.) to adjust the viscosity and concentration to obtain a coating solution. Then, this coating solution is spray-coated on the molded body obtained in the same manner as in Example 1, and the volatile solvent is dried and removed to form a surface coating layer having an average thickness of 10 μm. Manufactured.

(Comparative Example 1)
The molded body obtained in the same manner as in Example 1 without using surface coating with polyethylene wax was directly used as a tablet as a sample.

(Comparative Example 2)
N-heptane as a solvent was added to polyethylene wax (acid value 18 mgKOH / g, number average molecular weight 3000, product number HW-4252E, manufactured by Mitsui Chemicals, Inc.) to adjust the viscosity and concentration to obtain a coating solution. Then, this coating solution is spray-coated on the molded body obtained in the same manner as in Example 1, and the volatile solvent is dried and removed to form a surface coating layer having an average thickness of 60 μm. Manufactured. In this tablet, the thickness of the surface coating layer exceeds the upper limit of the thickness of the surface coating layer defined in the present invention.

(Comparative Example 3)
N-heptane as a solvent was added to polyethylene wax (acid value 18 mgKOH / g, number average molecular weight 3000, product number HW-4252E, manufactured by Mitsui Chemicals, Inc.) to adjust the viscosity and concentration to obtain a coating solution. Then, this coating solution is spray-coated on the molded body obtained in the same manner as in Example 1, and the volatile solvent is dried and removed to form a surface coating layer having an average thickness of 3 μm. Manufactured. In this tablet, the thickness of the surface coating layer is lower than the lower limit value of the thickness of the surface coating layer defined in the present invention.

  Next, the tablet of Examples and Comparative Examples was evaluated for weight reduction rate, surface appearance, spiral flow, gel time, and molded product appearance as described below. The results are shown in Table 1.

  Weight reduction rate (%): After putting 20 weighed tablets in a box and applying vibration for 5 minutes, the powder scattered from the tablet is removed and weighed again to determine the weight reduction rate (%) of the tablet. Calculated. In addition, this weight reduction rate becomes a parameter | index showing the ease of generating of the powder from a tablet, and it represents that generation | occurrence | production of the powder from a tablet is suppressed, so that a weight reduction rate is low.

  Surface appearance: The surface of the tablet evaluated for the weight reduction rate was visually observed to evaluate the degree of powder adhesion. In the table, “◯” indicates that the powder was hardly adhered, “△” indicates that the powder was slightly adhered, and “×” indicates that the powder was largely adhered. Show.

  Spiral flow (cm): When using a spiral flow measurement mold according to EMMI-I-66, 15 g of a tablet crushed sample was molded at a molding temperature of 175 ° C., a molding pressure of 7.0 Pa, and a molding time of 2 minutes. The length of the molded product was measured.

  Gel time (seconds): The time required for gelation of a sample obtained by grinding a tablet on a hot plate at 175 ° C. was measured.

  Appearance of molded product: The appearance of a molded product when a tablet was crushed into a disk shape having a molding temperature of 175 ° C., a molding pressure of 7.0 Pa, a molding time of 2 minutes and a diameter of 50 mm and a thickness of 3 mm was evaluated. In the table, “○” indicates that there was almost no dirt due to wax, “△” indicates that there was some dirt due to wax, and “×” indicates that there was much dirt due to wax. Show.

  As is clear from Table 1, the tablet of Comparative Example 1 that was not subjected to the surface coating with polyethylene wax was found to have a large weight loss due to vibration, and to have a lot of powder scattering, and the powder adhered to the surface was also Many are found to have poor surface appearance. Moreover, although the surface coating was performed, about the tablet of the comparative example 3 whose thickness is too thin as 3 micrometers, it is recognized that there is comparatively much scattering of powder and it is recognized that surface appearance is also not excellent. On the other hand, for the tablet of Comparative Example 2 where the thickness of the surface coating is too thick, although the powder scattering is small and the surface appearance is good, the spiral flow becomes longer, the gel time becomes longer, and the moldability decreases. It is recognized that

  On the other hand, about the tablet of Examples 1 and 2 which made surface coating predetermined thickness, it is recognized that there is little weight loss, a surface appearance is also favorable, and a moldability is also substantially favorable. In particular, for the tablet of Example 1 in which the acid value of the polyethylene wax is within a predetermined range, it is recognized that the molded product does not show dirt due to wax and the molded product appearance is also good.

The external view which shows the epoxy resin tablet for semiconductor sealing of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Epoxy resin tablet for semiconductor sealing, 2 ... Molded object, 3 ... Surface coating layer

Claims (4)

A step of tableting the epoxy resin composition for semiconductor encapsulation into a tablet to obtain a molded body,
And a step of performing a surface coating with an average thickness of 5 μm or more and 50 μm or less using polyethylene wax on the surface of the molded body. A method for producing an epoxy resin tablet for semiconductor encapsulation.   The method for producing an epoxy resin tablet for semiconductor encapsulation according to claim 1, wherein the polyethylene wax has an acid value of 10 mgKOH / g or more and 30 mgKOH / g or less and a number average molecular weight of 1000 or more and 5000 or less. A tablet-like molded article comprising an epoxy resin composition for semiconductor encapsulation;
An epoxy resin tablet for semiconductor encapsulation, comprising a surface coating layer formed on the surface of the molded body and made of polyethylene wax and having an average thickness of 5 μm to 50 μm.   4. The epoxy resin tablet for semiconductor encapsulation according to claim 3, wherein the polyethylene wax has an acid value of 10 mgKOH / g to 30 mgKOH / g and a number average molecular weight of 1000 to 5000.

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